Philosophy professor William B. Irvine opens his book on insults with a story. A man rubs the bald head of his friend and says, “Marc, your head feels as smooth as my wife’s ass.” The bald man reaches up and rubs his hand across the same spot. “So it does,” he says, “So it does.”

In A Slap in the Face, out this month, Irvine argues that evolution helps explain humans’ tendency to hurl “yo mama” jokes at one another. In this week’s Wednesday Words, we asked him about the history of invectives and why he thinks humans would be better off without them.

Let’s start with the most basic question. What is an insult?

If you say or do something that causes another person pain, it’s going to count as an insult. It could be an accidental insult. You could even have been trying to praise them. But I’m calling it an insult if, in fact, a word or action on your part harms another person.

You talk about the sundry ways we can insult each other, from burping to forgetting an anniversary. Would you say that verbal insults are the most powerful?

Breaking someone’s knee I guess counts as an extreme physical insult, and that would have a dramatic impact, but … it’s quite possible for a verbal insult to do more long term damage. Ten words uttered in ten seconds can destroy a relationship that has lasted for ten years. The thing to keep in mind is: they’re just words, but they have incredible destructive ability.

What is the secret to a really effective insult?

I say the highest form of insult is repartee. You take the insult and then you find a surprising way to turn the insult around. A classic example is Lady Astor saying to Winston Churchill, “If you were my husband, I would put poison in your coffee,” and he responds, “If you were my wife, I would drink it!”

How did the advent of language change the way we insulted each other?

It gave those of us who are weak but verbally agile a way to level the playing field. Yeah, that guy’s bigger than you are but you can make him look like a fool, and presumably that’s how [insults] got started. Animals kind of go through what we humans go through, only they do it with snarls and fights and bites and nips, just posturing. And presumably at some point, that’s how our evolutionary ancestors sorted themselves into dominance hierarchies.

What is the social role of insults today?

There’s this social hierarchy game that we’re engaged in. You would love for other people to admire you, to defer to you, to envy you even. And you don’t want anybody looking down on you. So … in what seem like casual conversations, we’re really staking out our turf and trying to rise and to get others to fall.

And how have insult techniques changed over time, from, say, Shakespeare’s time to now?

People have become less verbal. The vocabularies have shrunk dramatically. To come up with a good insult requires a certain degree of intellect, and if those things start disappearing, then the nature of the insults are going to change. The other thing that’s happened is that we live in an increasingly narcissistic society where people really are quick to unleash insults and are easily hurt by insults directed their way. … The really disappointing ones are those that just drop the f-bomb. That’s one level up from a barking dog.

In the book you argue that we shouldn’t let insults bother us. Why?

Most people think that insults are the problem. Insults are in fact a symptom of an underlying problem, that we’re programmed to play this social hierarchy game. It’s a game that can’t be won because if you’re below other people, you’ll feel bad. If you’re above them, they will start attacking you and you’ll feel bad. And if you stop playing, it dramatically enhances relationships. Once you stop, the insults lose their sting.

That seems like something that’s a lot easier to say you’ll do than to do.

It’s an example of where you’re trying to override your evolutionary programming … But it can be done. I’m in the experiment of doing it.

So how do you quit?

I watch myself in conversations. Start analyzing your own motives: why did I tell this person the following thing? Reread old emails and try to figure out how much of it is purely self-promotional. I wouldn’t regard myself as having succeeded entirely, but at least I’m trying.

Wednesday Words is a weekly column that delves into the way we wag our tongues and wield our pens.